feat(panel): add sponsor slots fed from sponsors.sanaei.dev

Monthly sponsor placements need to change without cutting a panel
release. Panels now read 3X/sponsors.json from the MHSanaei/sponsors
repo (GitHub Pages on sponsors.sanaei.dev) and show active sponsors in
four slots: an overview banner, a rotating sidebar card (max three), the
login page and a new Sponsors page that also lists open placements.

An entry shows only while enable is not false and until is in the
future; links must be https and logos are png/webp/jpg by name only.
The list is cached for an hour and the last good copy survives upstream
failures; logos are proxied through /sponsors/logo/:name with failures
cached, so CSP stays 'self' and admin browsers never reach a third
party. Admins can hide a slot for 24h. Under XUI_DEBUG the panel reads
a sibling ../sponsors/3X checkout so edits can be previewed before push.

frontend/src/components/command-palette/CommandPalette.tsx

@@ -13,6 +13,7 @@ import {
   ClusterOutlined,
   CodeOutlined,
   CopyOutlined,
+  CrownOutlined,
   DashboardOutlined,
   DatabaseOutlined,
   DiscordOutlined,
@@ -418,6 +419,12 @@ export default function CommandPalette() {
         keywords: ['api', 'api docs', 'swagger', 'rest api', 'endpoints'],
         icon: <ApiOutlined />,
       },
+      {
+        path: '/sponsors',
+        title: t('menu.sponsors'),
+        keywords: ['sponsors', 'sponsor', 'partners'],
+        icon: <CrownOutlined />,
+      },
     ];
 
     pages